Raise error on spaced UNIX-style flag with no value

core/flags/parsing.odin

@@ -1,6 +1,7 @@
 package flags
 
 import "core:container/bit_array"
+import "core:fmt"
 
 Parsing_Style :: enum {
 	// Odin-style: `-flag`, `-flag:option`, `-map:key=value`
@@ -71,9 +72,15 @@ parse :: proc(
 				return
 			}
 
-			for /**/; future_args > 0; future_args -= 1 {
+			for starting_future_args := future_args; future_args > 0; future_args -= 1 {
 				i += 1
 				if i == len(args) {
+					if future_args == starting_future_args {
+						return Parse_Error {
+							.No_Value,
+							fmt.tprintf("Expected a value for `%s` but none was given.", current_flag),
+						}
+					}
 					break
 				}
 				#no_bounds_check arg = args[i]

tests/core/flags/test_core_flags.odin

@@ -1055,6 +1055,23 @@ test_unix_double_dash_variadic :: proc(t: ^testing.T) {
 	testing.expect_value(t, s.varg[2], "5")
 }
 
+@(test)
+test_unix_no_value :: proc(t: ^testing.T) {
+	S :: struct {
+		i: int,
+	}
+	s: S
+
+	args := [?]string { "--i" }
+
+	result := flags.parse(&s, args[:], .Unix)
+	err, ok := result.(flags.Parse_Error)
+	testing.expectf(t, ok, "unexpected result: %v", result)
+	if ok {
+		testing.expect_value(t, err.reason, flags.Parse_Error_Reason.No_Value)
+	}
+}
+
 // This test ensures there are no bad frees with cstrings.
 @(test)
 test_if_dynamic_cstrings_get_freed :: proc(t: ^testing.T) {